WASHINGTON — The Obama administration’s bid to regulate greenhouse gases, after losing last year’s congressional debate over global warming, is making the Environmental Protection Agency the focus of Republican attacks on federal oversight.

The House plans to vote soon on a bill to weaken the EPA’s ability to regulate pesticides. And the Senate is poised to act on several proposals to limit the agency’s powers to regulate carbon dioxide and other heat-trapping gases blamed for climate change.

One Senate measure, backed by top Republicans and scores of business groups, would flatly ban such EPA oversight. Democratic alternatives would impose temporary bans or other partial approaches.

It’s possible that none of the Senate measures will draw the 60 votes needed to overcome filibusters and win passage. But at least one of them might attract enough support to embolden Republican House members, who could attach it soon to a large federal budget bill now dominating Congress’s attention.

The budget bill may be difficult to defeat because its collapse would trigger a partial government shutdown.

The GOP-controlled House voted in February to bar EPA regulation of greenhouse gases, which the administration strongly defends. Thirteen Democrats supported the ban.

Efforts by Democrats and environmentalists to thwart the Republican push show the degree to which the environmental movement has been thrown on the defensive by a GOP-corporate coalition that equates regulations with job losses.

The National Association of Manufacturers warned lawmakers and President Barack Obama this week “to carefully consider the severe economic impact these job-killing regulations will have on energy prices and on businesses and families across country.”

The group backed up its warning with a new TV and radio campaign attacking EPA regulations in Pennsylvania, Ohio, Michigan, Missouri, Maine and Arkansas. Each of those states has a senator facing a potentially difficult re-election race next year, and Obama is likely to compete hard in all but Arkansas.

The anti-EPA push has frustrated environmental groups. They had hoped to fare better with Democrats controlling the White House and Senate.

“Attempts to gut the Clean Air Act and handcuff the EPA are the result of new, anti-government House members who are acting in the interest of big polluter campaign contributors,” said the Sierra Club’s Melinda Pierce.

Senate Democrats are seeking a compromise EPA measure that might appeal to their colleagues from coal-producing states such as Pennsylvania and West Virginia, and from heavy manufacturing states such as Michigan and Ohio. Proposals include a two-year ban on EPA regulation of greenhouse gases, and a halt to California’s program to set more stringent vehicle emissions standards than other states follow.

Many environmentalists feel they are losing ground on multiple fronts. Scores of Republican lawmakers publicly question whether human activities, including burning coal to generate electricity, contribute to global warming. A large body of scientific evidence supports the claim.

Even in the wake of the recent Gulf oil spill, West Virginia mine tragedy, Wall Street meltdown and Japan’s struggle with tsunami-damaged nuclear plants, liberal groups have had little success in calling for more rigorous government regulations. The nation’s stubbornly high unemployment rate has made it easier for business groups to argue that regulations, of almost any stripe, impede growth and jobs.

Some Republicans are bothered by the attacks on the EPA, which GOP President Richard Nixon created in response to public alarm over dirty air, rivers and bays.

“The Senate is poised to vote on a bill that would, for the first time, ‘disapprove’ of a scientifically based finding, in this case that greenhouse gases endanger public health,” William D. Ruckelshaus and Christine Todd Whitman wrote in a Washington Post op-ed piece. Both were EPA administrators in Republican administrations.

In 2009, the Democratic-controlled House passed an Obama-backed bill to cap carbon emissions and allow businesses to buy and sell rights to emit greenhouse gases. But the Senate ignored the bill, and dozens of House Democrats paid a price for their votes in the 2010 GOP midterm victories.